FI70954C - FOER FARING FRAMSTAELLNING AV PAPPER - Google Patents

Abstract

In making paper from an aqueous papermaking stock, a binder comprising colloidal silicic acid and guar gum is added to the stock for improving the paper or the retention of the stock components so that the polution problems and the amount of valuable substances in the white water are reduced.The guar gum in amphoteric or preferably cationic and may form part of the binder complex in a mixture with cationic starch. The weight ratio of guar gum to Si0₂ or of guar gum plus cationic starch to SiO₂ is between 0.1:1 and 25:1.

Description

Method for making paper 70 9 5 4 Förfarande för framställning av papper

The invention relates generally to papermaking processes and, more particularly, to the use of a binder in a papermaking process, wherein the binder comprises guar gum and colloidal lead acid to produce paper having improved strength and other properties. In addition, such a binder provides well-improved levels of retention of added materials as well as papermaking fines.

There are currently a number of serious problems in the papermaking industry. First, the price of cellulose pulp has risen significantly and relatively little good quality pulp is available. Secondly, a number of problems, including those related to the disposal of papermaking waste and the ecological requirements of various administrations, have significantly increased papermaking costs. Finally, the cost of energy required to make paper has increased in concrete terms. As a result, the industry and its customers have two options: either to pay the high costs or, in concrete terms, to reduce the quantity and / or quality of the cellulosic fibers, leading to a deterioration in the quality of the finished paper product.

20 The industry has made several attempts to reduce the cost of paper products. In one solution, clay and other mineral fillers are added to the papermaking process to replace the fibers, but such additions have been found to reduce the strength and other properties of the resulting paper to an unsatisfactory extent. Likewise, the addition of such mineral fillers causes poor retention of the filler materials, e.g., they pass through the wire to such an extent that the level of the filler material rises in the wastewater, making wastewater treatment and material removal a serious problem. Various detention aids have been used to eliminate the detention problem, but their use has not been entirely satisfactory.

Attempts have also been made to use pulp types that are less expensive and of poorer quality, but this, of course, results in deterioration of paper properties and often produces additional fines that are not retained in the papermaking process and this again causes wastewater disposal problems.

5

Thus, the main object of the invention is to provide a binder system and method which provide improved properties in paper and which allow the use of minimum amounts of fibers to provide the required strengths and other properties. Another object of the invention is to provide a binder system and a method of using the same which concretely increase the strength and other properties of the paper compared to a similar paper made with known binders. Yet another object of the invention is to provide a binder system and method of using the same that maximizes the retention of mineral fillers and other materials in a sheet of paper when the binder is used in a pulp machine. Yet another object of the invention is to provide a paper having a high concentration of mineral filler and acceptable strength and other properties.

Other objects and advantages of the invention will become apparent from the following description and the accompanying drawings, in which Figures 1-8 show diagrams of the results obtained when testing sheets of paper made in accordance with the examples and which illustrate various aspects of the invention.

The present invention is based on the discovery of a binder and method of using it that concretely increases the strength and other properties of a paper product and allows substantial amounts of mineral fillers to be used in the papermaking process and maximizes retention of filler and cellulose fines in the sheet. This makes it possible to reduce the cellulosic fiber content of the sheet for a certain quality of paper and / or to reduce the quality of the cellulosic fibers used without compromising the strength and other properties of the sheet. Also, by using the principles of the invention, the amount of mineral filler can be increased without unduly degrading the strength and other properties of the resulting paper product. Thus, by reducing the amount of stock used to make a particular sheet, or by replacing the mineral filler in the stock, reducing the fiber content allows the energy required for pulping to be reduced as well as the energy required to dry the sheet. In addition, it has been found that the retention of mineral filler and fines is at a sufficiently high level to minimize waste-5 water problems.

In general, the system according to the invention uses a binder complex with two components, i. colloidal silicic acid and amphoteric or cationic guar gum. The weight ratio of guar gum to 10 SiO 2 in colloidal lead is greater than 0.1 and less than about 25.

The binder system of the present invention can be combined with other binder systems. When combined with a binder system of cationic starch and colloidal silicic acid disclosed in European Patent Application 81850084.5 (Publication No. 0041056), part of the guar gum is replaced by cationic starch, the weight ratio of guar gum to guar gum + between SiO 2 in colloidal lead acid is also greater than 0.1 and less than about 25.

20

Cationic and amphoteric guar gums are soluble in cold water, which is advantageous over most cationic starches that require hot water or boiling. Another advantage of amphoteric and especially cationic guar gums is that their reactive sites are more accessible than the reactive sites of cationic starch, which makes it possible to use smaller amounts of binder to achieve the same effect if guar gum is used. A probable explanation for this phenomenon is that guar gum molecules form straight chains, while several starch molecules form serum-like chains.

It has been found that after drying, the sheet has significantly improved strength properties when using the principles of the present invention. It has also been found that when mineral fillers such as clay, chalk and the like are used in the pulp, these mineral fillers are effectively retained in the sheet and do not have the degree of detrimental effect on sheet strength that can be observed without using the binder system of the invention.

Binders based on a combination of cationic substances and silicic acid have already been used in the manufacture of sheet products. This is described, for example, in U.S. Patent 3,253,978, which discloses an inorganic sheet using a combination of cationic starch and silicic acid, but in which flocculation is counteracted and the system operates at very high concentrations of silicic acid. In contrast to the present invention, this patent discloses that cationic starch need not gel the silica sol, although it tends to flocculate.

Gelling and flocculation are said to result in poor dewatering and adhesion to the wire and a reduction in the porosity of the sheet produced, thus counteracting flocculation and gelling with pH adjustments.

15

The papermaking process according to published Swedish patent application 8003948-0 and the corresponding European patent application 81850084.5 (Publication No. 0041056) uses a binder containing colloidal silicic acid and cationic starch. This papermaking also provides the excellent effects mentioned above, but in some cases may bring with it too high a concentration of cationic starch in the paper, resulting in an increase in the hardness of the paper, which in some cases is not appropriate. This disadvantage can be eliminated by using the binder system of the present invention.

25

Although the mechanism of pulp and paper formation and drying in the presence of a binder is not fully understood, it is believed that guar gum and colloidal silicic acid form a complex agglomerate bound together with anionic colloidal silicic acid and also containing cationic starch, if present. present in the binder, and that the guar gum becomes attached to the surface of the mineral filler, the surface of which is either completely or partially anionic. Guar gum and optional cationic starch are also associated with cellulosic fibers and fines, both of which are anionic. When dried, the bonding between the agglomerate and the cellulose-35 fibers results in extensive hydrogen bonding. This theory is supported in part by the fact that the zeta potential of the anionic mass moves to zero when using the binder complex n 70704 according to the invention, both the strength properties and the retention are improved.

We have found that when a binder system of the type described above is used, the effect of the binder system can be enhanced by the frequent addition of 5 colloidal silicic acid components, i. a portion of the colloidal silicic acid is first mixed with the stock and any mineral filler present, then the guar gum and cationic starch, if present, are added, and then the complex of the stock, filler (if present), silicic acid and guar gum / starch the agglomerate is formed and before the pulp is fed to the heating box of the papermaking machine, the remaining part of the colloidal silica is mixed with the pulp containing the complex agglomerate. This method of feeding colloidal silicic acid in two or more stages provides certain improvements in strength and other properties, but the most impressive improvement is an increase in retention of filler and papermaking fines. The reason for these improvements is not fully known, but it is believed that they result from the formation of complex filler-fiber-binder agglomerates that are more stable, i. that subsequent addition of colloidal silicic acid causes the agglomerates initially formed to bind together to form even more stable agglomerates that are less sensitive to mechanical and other forces in paper formation.

Based on the work done to date, the principles of the present invention are believed to be applicable to the production of all grades and types of paper, for example, printing grades, including newsprint, tissue paper, paperboard, liner and sack paper, and the like.

30 It has been found that the greatest improvements are observed when the binder is used with chemical pulps, such as sulphate and sulphite pulps, which come from both hardwood and softwood. Minor but very significant improvements occur with thermomechanical and mechanical stockings. It has been found that the presence of excess lignin in the wood pulp stock interferes with the effectiveness of the binder, so that such stocks may require either a higher proportion of binder or a higher proportion of other low lignin stock to achieve the desired result. (As used herein, the terms "cellulosic pulp" and "cellulosic fiber" refer to chemical thermomechanical and mechanical or wood pulp pulp and the fibers contained therein.) The presence of cellulosic fibers is necessary to achieve certain improved results of the invention resulting from the agglomeration and cellulosic fibers. Preferably, the finished paper should contain more than 50% cellulosic fibers, but smaller amounts of cellulosic fiber-containing paper can be made with significantly improved properties compared to paper made from a similar pulp without the binder agglomerate disclosed herein.

The mineral filler material that may be used includes any of the common mineral fillers having a surface that is at least partially anionic in nature. Mineral fillers such as kaolin, bentonite, titanium dioxide, gypsum, chalk and talc can be used satisfactorily. (The term "mineral fillers" as used herein means, in addition to the above materials, wollastonite and glass fibers 20 and also low density mineral fillers such as expanded perlite.) When the binder complex disclosed herein is used, the mineral fillers are substantially retained in the finished product and the paper produced is not than when no binder is used.

25

The mineral filler is normally added in the form of an aqueous slurry at the usual concentrations used for such fillers.

As mentioned above, the mineral fillers in the paper may be formed of or comprise a low density or fluffy filler. The possible addition of such fillers to conventional pulps is limited by factors such as the retention of the fillers in the wire, the dewatering of the pulp by wire, and the wet and dry strength of the resulting paper product. We have now found that the problems caused by the addition of such fillers can be avoided or substantially eliminated by using the binder complex of the present invention, which also allows the addition of higher than normal proportions of such fillers to provide specific properties of the paper product. Thus, by using the binder complex of the invention, it has become possible to produce a paper product with a lower density and thus higher stiffness at the same basis weight while maintaining the strength properties of the paper product (such as modulus of elasticity, tensile index, tensile energy absorption and surface fiber release resistance).

As indicated above, the binder comprises a combination of colloidal silicic acid and amphoteric or catholic guar gum, optionally mixed with cationic starch. Colloidal silicic acid may exist in various forms, for example it may be in the form of sols of polysilicic acid or colloidal silicic acid, although the best results are obtained using sols of colloidal silicic acid.

Polysilicic acid can be prepared by reacting water glass with sulfuric acid by known methods to obtain up to about 100,000 molecular weights (SiO 2). However, the resulting polysilicic acid-20 po is unstable and difficult to use and poses a problem such that the presence of sodium sulfate causes corrosion and other problems in papermaking and wastewater removal. Sodium sulfate can be removed by ion exchange using known methods, but the resulting polysilicic acid is unstable and, without stabilization, deteriorates upon storage. Salt-free polysilicic acid can also be prepared by direct ion exchange of dilute water glass.

Although substantial improvements in both strength and retention are observed with a binder containing polysilicic acid and amphoteric and especially cationic guar gum, optionally mixed with cationic starch, first-class results are obtained by using guar gum with colloidal silicic acid in the form of a solution containing about 2- 60% by weight

SiO 2 and preferably about 4-30% by weight SiO 2.

35 The surface area of the colloidal silicic acid in the solution should preferably be about 50-2 2 to about 1000 m / g and more preferably about 200 to about 1000 m / g, with the best results being observed when the surface area is about 1000 m / g. 300 - about 700 m / g. The silicic acid solution 8 70954 is stabilized with an alkali with a molar ratio of SiO 2, tM 2 O of 10: 1 to 300: 1, preferably 15: 1 to 100: 1 (M is an ion selected from the group consisting of Na, K, Li and NH 4). It has been found that the size of the colloidal silica particles should be less than 20 nm and preferably the average size should be about 10-1 nm.

2 5 (A colloidal silica particle with a surface area of about 550 m / g requires an average particle size of about 5.5 nm).

In fact, an attempt is made to use a silica solution with colloidal silica particles. having a maximum active surface area and a well-defined small size, usually about 4-9 nm.

Silicic acid solutions meeting the above definitions are available on the market from a variety of sources, including Nalco Chemical Company, Du Pont & de Nemours Corporation, and the applicant of this invention.

15

The guar gum used in the binder of the present invention is an amphoteric or cationic guar gum. Guar gum occurs naturally in the seeds of the guar plant (e.g., Cyamopsis tetragonalobus). The guar molecule is a substantially straight-chain mannan branched at fairly regular intervals on individual galactose units with alternating mannose units. The mannose units are linked together by ε- (1-4) -glycoside bonds. The galactose branch is obtained by an o <- (1-6) bond. Cationic derivatives are formed by the reaction between the hydroxyl groups of polygalactomannan and reactive quaternary ammonium compounds. The amount of substitution of the cationic groups is suitably at least 0.01 and more preferably at least 0.5 and may be as high as 1.0. A suitable range may be 0.08-0.5. The molecular weight of guar gum is assumed to be 100,000 to 1,000,000, generally about 220,000. Suitable cationic guar gums are mentioned in published European patents EP-A-30 0,018,717 (EP application 80300940.6) and EP-A-0,002,085 (EP application 78200295.0) in connection with shampoo preparations and fabric softeners, respectively. Natural guar gum, when used as a paper chemical, provides improved strength, reduced dust formation and better paper formation. The disadvantage of natural guar gum is that it makes the dewatering process more difficult and thus reduces the production efficiency or increases the need for drying. Admittedly, these problems have been largely avoided with the introduction of chemically modified guar gums, n 9 70954 which are amphoteric or cationic. However, the cationic or amphoteric guar gums on the market have not previously been used in the types of binder complexes used in accordance with the present invention. There are commercially available guar gums with different degrees of cation-5 ringing and also amphoteric guar gums.

Amphoteric and cationic guar gums that can be used in the present invention are commercially available from a variety of sources, including Henkel Corporation (Minneapolis, Minnesota, USA) and Celanese Plastics 10 & Specialties Company (Louisville, Kentucky, USA) under the trademarks GENDRIV and CELBOND.

If the cationic starch is mixed with guar gum for use in the binder of the invention, the cationic starch may be derived from starches derived from some common starch-producing materials, e.g., corn starch, ammonium starch, wheat starch, potato starch, rice starch, by known methods and may have varying degrees of substitution up to 0.1. The best results are obtained when the degree of substitution (d.s.) is about 0.1-0.05 and preferably about 0.02-0.04 and especially above about 0.025 and below about 0.04. Although several ammonium compounds, preferably quaternary, are used in the preparation of cationized starches for our binder, we prefer to use cationized starch prepared by treating the base starch with 3-chloro-2-hydroxypropyl-trimethylammonium chloride-2,3-ethoxypropyltrimethylammonium chloride by ds is 0.02-0.04.

In the papermaking process, the binder is added to the pulp before the paper product is formed in the papermaking machine. The two ingredients, colloidal silica ingredients and guar gum (optionally mixed with cationic starch) can be mixed together to form an aqueous slurry of a binder complex containing silica and guar gum (and optionally cationic starch) and then added and thoroughly blended into the papermaking pulp. However, this method does not produce maximized results, especially if cationic starch is present. Preferably, a complex of silicic acid and guar gum and optionally cationic starch is formed in situ in the papermaking pulp. This can be accomplished by adding the colloidal silica component in the form of an aqueous sol and adding the guar gum and any cationic starch in the form of an aqueous solution separately to the pulp in a mixing tank or system mix where the two components are dispersed with the papermaking ingredients. and papermaking ingredients simultaneously.

Even better results are obtained if the colloidal silicic acid component is added to the pulp portion and mixed thoroughly with it, after which the pulp preparation is completed and the cationic starch component is added and mixed thoroughly with the pulp before forming the paper product.

15

In the case where a mineral filler has to be added to the pulp, it has been found that the mineral filler is slurried in water with colloidal silica, or in increasing doses of the silica component, with gum and possible cationic starch.

Thereafter, with increasing increments of the colloidal silica component, the remainder or portions of the colloidal silica component are thoroughly mixed with the pulp after the initial agglomerate has been formed and before or at the same time as the pulp is introduced into the heating box. The initial addition of colloidal silicic acid should comprise 20 to about 90% of the total amount to be added and then after the initial agglomerate is formed the remaining portion should be added before forming the sheet. The initial addition of Mie-30 plum should comprise from about 30% to about 80% of the colloidal silicic acid component.

It has been found that in the papermaking process using the binder complex described herein, the pH of the pulp is not overly critical and may be 4-9. However, pH ranges above 9 and below 4 are not desirable.

Il n 70954

Other paper chemicals such as finishes, alum and the like may be used, but care should be taken that the level of these substances is not high enough to interfere with the formation of silicic acid and guar gum and possibly cationic starch agglomerate and that the level of circulating effluent 5 does not become too high. that it interferes with the formation of the binder agglomerate. For this reason, it is usually better to add the substance at a point in the system after the agglomerate has been formed.

According to the invention, the weight ratio of amphoteric or cationic guar gum to the colloidal silicic acid component should be 0.1: 1 to 25: 1. The same weight ratio applies if part of the guar gum has been replaced by cationic starch. Preferably, this ratio is 0.25: 1 to 12.5: 1.

The amount of binder used will vary depending on the desired effect and the properties of the particular ingredients selected in the preparation of the binder. For example, if the binder contains polysilicic acid as a colloidal silicic acid component, more binder is required than if the colloidal silicic acid component is a colloidal silicic acid sol having a surface area of 300-220,700 m / g. Similarly, if cationic guar gum d.s. is, for example, 0.3 compared to it if its d.s. is 0.5, more binder is required assuming that the colloidal silica component is unchanged.

In general, when the pulp does not contain a mineral filler, the level of binder 25 may be 0.1-15% by weight and more preferably 0.25-5% by weight based on the weight of the cellulosic fibers. As highlighted above, the efficiency of the binder is higher with chemical stockings, so that less binder is required with these stockings to achieve a certain effect than with other types. In the case where a mineral filler is used, the amount of binder may be based on the weight of the filler material and may be 0.5 to 25% by weight and usually 2.5 to 15% by weight of the weight of the filler.

The invention is explained in more detail by the following examples.

35 These examples illustrate different grinding methods and the properties of the finished products. The following standards have been used for various purposes: 12 70954

Grinding in a Valley Hollander SCAN-C 25:76

Grinding degree:

Canadian Standard Freeness Tester SCAN-C 21:65

Schopper-Riegler SCAN-C 19:65 5 Sheet etching SCAN-C 26:76

Square weight SCAN-P 6:75

Density SCAN-P 7:75 Filler content SCAN-P 5:63

Tensile index SCAN-P 38:80 10 Z-strength Alwetron

Ash content (fly ash) Greiner & Gassner GmbH, Munich

Traction energy absorption index SCAN-P 38:80

When testing the produced sheets, they were first conditioned at 20 ° C in air with a relative humidity of 65%.

The retention measurements shown in the examples were performed by means of a so-called dynamic dewatering vessel ("Britt vessel") equipped with a drain pump and a measuring glass for collecting the first 100 ml of ke-20 water. A divided dewatering vessel with a wire (40 M) with a mesh size of 310 μm was used for the measurements. The suction rate was controlled by different diameter glass tubes and was 100 ml / 15 s in the experiments. The following measurement method was used: 1. 500 ml of the stock suspension was added with stirring at 1000 rpm and timing was started.

2. After 15 seconds, colloidal silica and filler were added. The total solids content (fibers + filler) should be 0.5%.

3. After 30 seconds, guar gum and / or cationic starch were added.

30 4. After 45 seconds the suction was started.

5. The first 100 ml of water was collected and filtered through a weighed filter paper. The filter paper was from Grycksbo-Munktell, Sweden, with a grade of 00 and was able to retain very fine granular fines, e.g., cold precipitated barium sulfate. The filter paper had a mesh size of 80 g / m 2 and a filtration rate of 150 ml / min

According to Hertzberg.

6. The filter paper was dried, weighed and incinerated.

13 70954 7. The arrest was calculated.

This retention measurement method has been proposed by K. Britt and J.E. Unbehend in Research Report 75, 1/10 1981 by Empire State Paper 5 Research Institute ESPRA, Suracuse, N.Y. 13210, USA).

The following examples used commercially available guar gum, clay and lime as well as cationic starch. In addition, market-based restraints were used as a comparison.

10

The chalk "SJÖHÄSTEN NF" used in the examples is a natural, high-quality calcium carbonate with an amorphous structure and is marketed by Malmökrita Swedish Whiting Company Limited, Malmö, Sweden. The C-grade clay and Superfill clay used are kaolin marketed by English 15 China Clay Limited, United Kingdom.

The different types of guar gum used are as follows: GENDRIV 158 and 162 are cationic guar gums, GENDRIV 58 with moderate, and GENDRIV 162 with strong cationic activity. Both are marketed by Henkel Corporation, Minneapolis,

Minnesota, USA.

CELBOND 120 and CELBOND 22 are types of guar rubber marketed by Celanese Plastics and Specialties Company, Louisville, Kentucky, USA. CELBOND 120 is an amphoteric guar gum with both cationic and anionic properties.

CELBOND 22 is a low substituted cationic guar gum with added quaternary ammonium groups.

PERCOL 140 is a cationic polyacrylamide used as a retention aid and marketed by Allied Colloids, UK.

PERCOL E24 is an anionic polyacrylamide used as a retention aid and marketed by Allied Colloids, United Kingdom.

The concentrations shown in the following examples are all calculated on a dry weight basis.

35 70954 EXAMPLE 1

In the laboratory wire model, handmade sheets were prepared from different pulps having the compositions shown in Table 1. For the pulp, a fully bleached softwood sulfate pulp made of pine and ground in a Vailey cholester to a CFS of 470 was used. Kaolin (C-clay, English China Clay Limited) was used as a filler and added as a clay slurry at a concentration of 100 g / l. The pH of the pulp was adjusted to 4.4 using sulfuric acid. A combination of cationic 10 guar gum (GENDRIV 162) and a silicic acid sol was used as a binder and the comparison was performed on reference masses 1-3 containing the already known retention aid PERCOL 140 (cationic polyacrylamide). The silica sol 2 used was a 1.5% silica sol with a surface area of 503 m / g and a SiO 2: Na 2 O ratio = 35. In the experiment, the clay slurry was first treated with a silica sol for 0.5 hours. To prepare the pulp, the stock was metered in portions, and then the clay slurry and the silica sol were mixed with it. An aqueous solution of cationic guar gum (0.5% concentration) or PERCOL (0.01% concentration) was then added, after which the pH was adjusted to 4.4 using sulfuric acid. Finally, sheeting was performed.

The properties of these obtained hand sheets are shown in Table 1. The results are also shown in the diagram in Figure 1. It can be seen from the table and the diagram that the use of the binder complex according to the invention makes it possible to increase the filler content while keeping the tensile index the same.

25 EXAMPLE 2

In the laboratory wire model, handmade sheets were made from different pulps, the compositions of which are shown in Table 2 and which had the properties shown in Table 2. The same pulp and filler were used as in Example 1, with the proportions of pulp 8 being 70% clay and 30% pulp and the other pulps 30% clay and 70% pulp. The binder was formed from cationic guar gum, which was added as a 0.5% aqueous solution and consisted of either GENDRIV 162 with a nitrogen content of 1.5% or CELBOND 22 with a nitrogen content of 0.95%. As the silica sol, a 1.5% silica sol having a specific surface area of 2,550 m / g and a SiO 2: Na 2 O ratio of 45 was used. No chemical additives were used in Comparative Samples 7 and 8. Masses 9 and 10 are in accordance with the invention.

Il 15 70954 The pH was adjusted to 7.0. The dose order in the preparation of the pulp was the same as in Example 1.

This example shows that both highly substituted catholic guar-5 rubber (pulp 10) and low substituted catholic guar rubber (pulp 9) produce increased filler content of the paper.

EXAMPLE 3 In a laboratory wire model (Formette Dynamique), handmade sheets were prepared from various pulps having the compositions shown in Table 3. In this example, a slurry with 50% birch sulfate and 50% pine sulfate and a degree of grinding of 20% SR was used. The filler consisted of Clay clay in the form of a 10% aqueous slurry. An aqueous solution of 15 catholic guar gum (GENDRIV 158) and a 1.5% silica sol was used as a binder and the silica sol had a surface area of 530 m / g and a ratio of 510 ^ 320 = 35. In the blank tests (masses 11-13) no used no chemical additives. In Comparative Tests 14-16, only guar gum was used, but no silicic acid sol. Masses 17-19 were prepared according to the invention. Pulp preparation and sheet formation were performed according to Example 1, the pH was adjusted to 7.5.

Table 3 shows the pulp compositions and test results. The test results are also shown in the diagrams of Figures 2 and 3, where curve A relates to nullates-25, curve B relates to comparative tests and curve C relates to the invention with the guar-rubber + silicic acid sol binder complex. It can be seen from Figure 2 that although the addition of guar gum produced an increase in filler content at an equal tensile index, the improvement was significantly greater with the present invention. It can be seen from Figure 3 that a large improvement in the tensile energy absorption index is achieved by the present invention.

EXAMPLE 4 In this example, handmade sheets were prepared in a laboratory wire model using pulps made of fully bleached pine sulfate with a degree of grinding of 470 CSF. Clay was used as a filler in the form of a 10% aqueous slurry. The weight ratio of stock to filler was 70:30. The binder consisted of 0.5% aqueous solution of guar gum GENDRIV 162 and 1.5% silica sol. The surface area of the silicon acid acid sol was 500 m / g and the ratio SiO 2: Na 2 O * 35. Only the guar gum shown was used in the control tests. During the preparation of the pulp, the pH was adjusted to 4.4. In the preparation of pulps 21-25, the filler and the silica sol were mixed before they were mixed into the stock. After mixing the filler and the stock, cationic guar gum was added, the pH was adjusted with sulfuric acid, and finally a sheet was formed. The compositions of the masses and the Z-strength determined according to Alwetron are shown in Table 4.

EXAMPLE 5

Similarly, in this example, handmade sheets were made in a laboratory-15 wire model. The stock consisted of fully bleached pine sulphate stock with a degree of grinding of 470 CSF. The filler was C-clay (10% aqueous slurry). In the pulps 30-32 of the invention, the binder consisted of cationic guar gum GENDRIV 162 (0.5% aqueous solution), 1.5% silicic acid salt with a surface area of 500 m / g and a ratio of SiO 2: Na 2 O = 35. Comparative Experiments 26-29 used PERCOL 140 (0.01%) as a retention aid. The pH of the pulps 26, 27, 28.30 and 31 was adjusted to 4.4, while the pH of the pulps 29 and 32 was adjusted to 9.0.

In preparing the pulps, the stock was first divided into portions and then the filler-25, which, using a silica sol, had been pretreated with a silica sol.

Guar gum was then added, when used, the pH was adjusted with sulfuric acid at masses 26-28, 30 and 31 and with sodium hydroxide at masses 29 and 32.

As can be seen from Table 5 and Figures 4 and 5, it is possible by using the present invention to increase the filler content while maintaining a certain tensile index and to obtain the same advantageous effect on Z-strength (Figure 5).

35 EXAMPLE 6

In the laboratory wire model, handmade sheets were made from a variety of 17,70954 pulps made from fully bleached pine sulfate stock with a degree of grinding of 470 CSF. A 10% aqueous slurry of chalk (SJÖHÄSTEN NF) was used as filler. The binder consisted of cationic guar gum GENDR1V 162 (0.5%) and 1.5% silicic acid sol with a surface area of 550 m / g and a SiO 2 iNa 2 O = 40 ratio. PERCOL 140 was used as a control. (0.01%) in masses 33-35. The pH was adjusted to 7.0. The pulps were prepared according to the above examples. The composition of the pulp and the test results are seen in Table 6 and the diagram in Figure 6. As can be seen in Table 6 and Figure 5, the binder composition of the invention provides a significant increase in strength when using chalk as a filler.

EXAMPLE 7 This example is a retention test using a dynamic dewatering-15 vessel (Britt vessel). The fibrous part of the pulp consisted of 25% fully bleached hardwood sulphite pulp with a degree of grinding of 25 ° SR, 25% fully bleached pine sulphate pulp with a degree of grinding of 25 ° SR and 50% of thermomechanical pulp with an ISO whiteness of 70 and a degree of grinding of 80 CSF . The latter stock contained wastewater and all stock was taken from a paper mill. A 10% aqueous slurry of Superfill clay (English China Clay Limited) was used as a filler. The binder consisted of 0.5% solution of cationic guar gum GENDRIV 162 and 1.5% silica sol.

2

The surface area of the sol was 550 m / g and the ratio SiO 2: Na 2 O = 40. Alum was used in Comparative Test 30 (1% solution), while Comparative Test 40 is based on the above-mentioned Swedish patent application 8003948-0 and the corresponding published European patent application ΕΡ-Λ. -0041056 binder using a binder agglomerate of silica sol and cationic starch (0.5% concentration). The mode of operation of these arrest tests is described above. In the tests, the pH of the pulp was adjusted to 5.5 and the speed of the mixer 30 was 1000 rpm.

It can be seen from Table 7 that improved filler retention is achieved when transported from the alum of Reference Sample 39 to a combination of silica sol and cationic starch in pulp 40. It is further seen that the invention 35 provides further improvements in filler retention, although a smaller total amount of chemicals added was used.

18 70954 EXAMPLE 8 This example also applies to retention tests in a dynamic dewatering vessel (Britt vessel). In this case, the pulp was made from pulp with 5% 80% wood pulp with a degree of grinding of 100 CSF and 20% pine pulp.

pulp pulp with a degree of grinding of 470 CSF. Clay (10% aqueous slurry) was used as a filler in an amount of 20% by weight. Cationic guar gum GENDR1V was used as a binder for pulps 44 and 45

162 and a 0.5% solution of 1.5% silicon apole. The surface area of the silicic acid sol 2 was 505 m / g and the ratio SiO 2 Na 2 O = 35. The reference mass 43 used PERCOL 140 (0.01%) as a retention aid, while the mass 42 was a blank without chemical additives. In all cases, the pH was adjusted to 5.4 and the stirrer speed was 1000 rpm.

It can be seen from the results in Table 8 that the invention (masses 44 and 45) provides significant improvements in filler retention.

EXAMPLE 9 In this example, a mixture of amphoteric or cationic guar gum and cationic starch together with a silica sol was studied to form a pulp binder complex. The dosages of the different chemicals were chosen so as to provide a constant chemical cost at the current prices of the chemicals. The following types of guar gum were used in the tests: 25

GENDRIV 162 cationic 1.5% N

GENDRIV 158 cationic 1.0% N

CELBOND 22 cationic 0.75% N

CELBOND 120 amphoteric 0.95% N

A starting ratio of 3:10 was used as the ratio of silica sol to cationic starch, as this is the general dosage for the binder system according to SE patent application 8003948-0 and the corresponding published European patent application EP-A-0041056.

The pulp composition of these tests was 70% by weight of fully bleached pine sulphate with a degree of grinding of 340 CSF and 30% of Clay. Clay was added as 35 10954 as a 10% aqueous slurry, guar gum as a 0.5% aqueous solution, cationic starch as a 0.5% aqueous solution and a sol as 1.5% 2 silica sol with a surface area of 505 m / g and the ratio SiO 2 '. Na 2 O = 35. The ds of cationic starch was 0.047%. The pH of the pulp was adjusted to 7.0.

5

The sheets prepared in the laboratory wire model had the properties shown in Table 9 and Scheme 7. The results show that blends of cationic starch and guar gum are useful for achieving improvements in paper quality. It could be seen that the paper tends to become softer as the proportion of guar gum in the binder composition increases.

EXAMPLE 10 This example relates to retention tests using pulp from a commercial papermaking machine producing supercalendered magazine paper. Retention tests were performed in a dynamic dewatering vessel (Britt vessel). The pulp used in the tests contained 20% by weight of fully bleached hardwood pulp, CSF 672, 50% by weight of wood chips, CSF 55 and ISO whiteness 70, 15% by weight of waste paper, CSF 107, and 20% by weight of C-grade clay.

The pulp was diluted with filtered water coming from the disc filter of the papermaking machine so that all interfering organic substances were present. The concentration of the diluted mass was 5 g / l. The pH was 6.2.

The diluted mass was poured into a Britt vessel and the stirrer was started at 30 (speed 1000 rpm). Within 15 seconds, all, alum, guar gum (GENDRIV 162, 1.5% aqueous solution) and 1.5% silicic acid sol Ί (area approx. 550 nf / g and SiO 2: Na 2 O = 35) was added sequentially to a Britt vessel. Water suction was then initiated to detect the above arrest. The test results are shown in Table 10.

It can be seen from Table 10 that there was a significant increase in both overall retention and filler retention using the invention (mass 60) and that the increase was not cumulative but synergistic.

EXAMPLE 11 5 This example relates to a retention test in which the strength of the flakes formed in the pulp was evaluated by varying the rotational speed of the mixer grain in a dynamic dewatering vessel (Britt vessel). Pulp from a commercial papermaking machine used to produce low density coated wood paper or LWC-10 paper was used.

The pulp contained 39% by weight of wood chips, 74 ° SR, 30% by weight of pine sulphate pulp, 22 ° SR, 21% by weight of waste paper, 66 ° SR and 10% by weight of C-grade clay.

The pulp was diluted with rising water from a counting-20 funnel connected to a papermaking machine. The chemical oxygen demand (COD) of this water was 1300 mg / l and the conductivity was 3000 μS / cm.

In all tests 61-69, 1% by weight of alum was added to the diluted mass which had been poured into a Britt vessel and stirred at the indicated rate for 15 sec. before the addition of any retention aid or binder. In tests 61, 62 and 63, the retention aid was then added and mixed for 15 sec. before the suction of water from the pulp was started. In tests 64-69, a silica sol was first added and mixed for 15 sec, and then guar gum was added and mixed for 15 sec. before the suction of water from the pulp was started. The pH was adjusted to 6.5 and the retention aid added in tests 61, 62 and 63 was PERCOL E24.

As can be seen from the test results in Table 11 and Figure 8, the invention substantially improves filler retention at all agitator speeds. Judging from the Tu-35 logs, the binder complex of the invention responds to increasing agitator rates in approximately the same manner as a known retention aid, albeit at substantially higher retention levels.

Il 21 TABLE 1 70954

Sulpun Silica- Cation- PERCOL Square- Density Tensile- Filling-proportion of posolene 140 mass .3 index-

Mass of clay, guar gum, 2 g m si content

mass ° ^ g Nm / g ORAL

% 1. Value 90:10 - - 0.025 72.4 630 63.9 2.9 2. Value * 70:30 - - 0.025 5Θ.Θ 620 47.8 11.6 3. Value 50:50 - - 0.025 69.0 590 34.5 17.6 4. Cc. 90:10 0.2 0.32 - 75.6 626 58.6 6.3 5. Biscuit. 80:20 0.2 0.32 - 70.1 630 50.8 12.0 6. Biscuit. 70:30 0.2 0.32 - 65.0 638 38.4 20.5 TABLE 2 -------; - 1 -----

Silica Acid Cation Density Tensile Tear Filling Mass Solar Mass (Mass., 2 Index-Guar-Rubber 2 g / Si Dex Concentration% 8 m Nm / g TiNm / g Oral% 7 . Comparison ~ "67 * 0 600 64.2 13.4 5.4 8. Comparison“ ”69.0 590 34.5 12.0 17.6 9. CELBOND 22 0.3 0.5 70.0 715 71.0 11.6 8.9 10. GENDRIV 162 0.3 0.5 86.0 595 40.0 13.2 26.8 TABLE 3 22 70954

Silicon Cation Square J Density Tensile Tensile Filling Acidic mass of stock 'index energy content in riclSS i *.

salts of guar. 2 kg / m si an abittoi- clay, · g / m! .

Kumi. sorption in mass% z Nm / «index z ______ £ / kg ___ 11 Zero - - 85.3 561 52.0 803 0.0 100: 0 12 Zero - - 85.2 572 35.8 411 13.4 83:17 13 Zero - - 86.1 607 23.6 197 29.1 63: 35 14 Rev. - 1.0 89.5 585 58.6 960 0.0 100: 0 15 Rev. - 1.0 '86 .6 618 44.7 542 13.6 83: 17 16 Rev. - 1.0 85.4 652 31.0 293 29.0 65:35 17 Bisc. 1.0 1.0 90.8 605 71.3 1639 0.0 100: 0 -3 Cc. 1.0 1.0 90.1 626 50.8 763 15.0 83:17 -9 Biscuits 1.0 1.0 89.7 660 35.6 392 30.2 65:35 ---- 1 — I —----! TABLE 4 --TT - -; -; - · -; —-—; -; -

Ratio Silica- Cation- Square- Density Z-strength Filler- guarzolic mass. 3, concentration ,, rubber: guar, 2 kg / m kFa.

^ in 6. g / m% salt% rubber _ / o 20 0.32 65.6 631 417 22.2 21 10.7 0.03 0.32 68.0 667 420 23.0 22 3.2 0.10 0.32 66.5 646 431 24.5 23 1.6 0.20 0.32 68.6 647 424 24.1 24 0.8 0.40 0.32 67.9 641 475 24.9 25 0.4 0.80 0.32 66.5 j 652 507 22.4 23 TABLE 5 7095 4 pH PER- Silicon— Cation— Square— Density Tensile— Z — Strength Acidic Mass of Filler Pulp, <3 Index Substance

Mass j 140 sol guar- ^^ 2 - ® si 3 pitoi-clay 7 7 rubber Nm / g in oral mass

I / 0 A

'* 4 - 1 1 f 1 -' 1 ........ 1 '' '1 | 26 Vert.! 4.4 0.025 {- - 72.4 630 63.9 590 2.9 90:10 'i 27 "14.4 0.0251 - - 59.0 605 48.4 489 9.0 80:20 28" 14.4 0.025 - - 60.3 590 38.4 445 15.4 70:30 29 ”9.0 0.025 - - 69.0 590 34.5 416 18.0 70:30 30Keks. 4.4 - 0.2 0.32 75.6 620 58.6 600 6.4 90:10 31 ”4.4 - 0.2 0.32 65.8 628 38.4 458 20.9 70:30 32” 9.0 - 0.2. 0.32 73.6 624 30.4 404 26.7 70:30 TABLE 6 I ------- I PERC0L Silicon Cation-Neutral Density Z-strength T ^ te_ SulPun 140 acidic mass 3 substance proportion M sol guar- 2 kg / ra kPa in the concentration of clay in the amount of rubber g / m in the mass%%% 33 Value 0.023 - - 73.1 619 538 4.1 90:10 34 Value 0.025 - - 58.6 592 502 9.4 80:20 35 Value 0.025 - - 66.5 588 372 16.6 70:30 36 Biscuits. - 0.2 0.32 76.6 649 578 4.7 90:10 3 / Bc. - 0.2 0.32 62.6 591 480 16.5 80:20 38 Biscuits - 0.2 0.32 65.0 590 400 26.0 70:30 TABLE 7 j Silicon- Cation- Cation- Alum Filling- Pulp acidic j substance content iMass sol guar gum starch- 0 retention in clay jj lys „pulp ________% ___ i__ 39 Vert. - - 0.3 37.0 80:20 40 Vert 0.17 - 0.58 - 42.5 80:20 41 Biscuits 0.17 0.27 - - 54.1 80:20 TABLE 8 24 70954

Silicon Cationic PERCOL Filler

Mas acid guar gum 140 retention SOOli% X z __% ____ 42 Zero test “~ 11.5 ij 43 Comparison ~” 0.025 23.0 j 44 Invention 0.05 0.08 - 30.0 45 Invention 0.2 0.32 - 47.0 TABLE 9 -------- ----- ... .... .. .. - - - 1 - „, Cation- Square- Traction- Filling- Ti-

Pn- Guar-kumx. . ,,. , ninen mass index density „appo ———— 2 si pitoi-,, 3

Mass of salts g / m kg / m _. Broth, mouth

Type Nm / g% s%% 1 2 3 4 5 6 7 8 9 10 11

Translation - - - - 60.7 64.0 5.3 615 2

Vert. 0.3 - - 1.0 87.1 49.0 22.5 624 3

Keks. 0.3 GENDRIV 162 0.5 - 84.2 39.5 26.8 608 4 49 Biscuit. 0.3 "0.3 0.4 83.2 44.0 25.2 610 5

Keks. 0.3 "0.15 0.7 81.8 47.0 24.1 601 6 51 Inventory 0.3 CELBOND 22 0.5 - 69.4 72.5 8.9 718 7 | 52 Inventory i 0.3 H 0.3 0.4 78.2 62.0 17.3 740 8

Keks. : 0.3 "0.15 0.7 80.7 55.5 21.7 745

1 I

9

Keks. 0 * 3 CELBOND 120 0.5 - 73.1 64.0 12.4 709 j 10

Keks. 0.3 ”0.3 0.4 72.7 61.0 19.3 727 11, 56 Biscuit. 0.3 "0.15 0.7 79.8 59.0 19.0 745 25 TABLE 10 70954

Aluna Guar- Silica- Total- Filler-

Mass rubber sol retention concentration% 7 1 1 1 57 Comparison 1 53.7 19.5 58 Reference silicic acid sol 1 - 0.2 55.0 19.7 59 Reference guar gum 1 0.3 ~ 63.8 42.5 60 Invention 1 0.3 0.2 70.1 52.8 TABLE 11

Mixer- PERC0L Silica Guar- Filler-

Ma.SSa men additive ^ rubber content speed% °% 7 rpm 1 2 3 4 5 6 7 8 9

Value 600 0.02 - - 22.0 2 "800 0.02 - - 10.0 3" 1000 0.02 - - 6.5 4

Guar gum 600 - - 0.5 42.0 5 "" 800 - - 0.5 18.0 6 M "1000 - - 0.5 17.5 7

Invention 600 - 0.2 0.5 59.5 8 63. "800 - 0.2 0.5 39.0 9" 1000 - 0.2 0.5 29.5

Claims (12)

A papermaking process, wherein an aqueous papermaking stock containing a cellulose stock is formed and dried, characterized in that a binder containing colloidal silicic acid and cationic or amphoteric guar gum is added to the pulp prior to sheet formation, wherein the ratio of guar gum to SiC is 0.01: 1 to 25: 1, preferably 0.25: 1 to 12.5: 1. Process according to Claim 1, characterized in that the binder also contains cationic starch having a degree of substitution of at least 0.01 and at most 0.1, preferably from about 0.01 to about 0.05 and in particular from about 0, O 2 to about 0.04, wherein the cationic starch, guar gum and colloidal silicic acid are mixed in a weight ratio (cationic starch + guar gum) of CH 2 O 2 of 0.1: 1 to 25: 1, preferably 0.25: 1 to 12.5: 1. Process according to Claim 1 or 2, characterized in that the colloidal silicic acid is arranged as a colloidal silicic acid sol having a surface area of about 50 to about 1000 m 2 / g, preferably about 300 to about 700 m 2 / g. Process according to Claim 1, 2 or 3, characterized in that the pH of the pulp is maintained in the range from about 4 to about 9. Process according to one of Claims 1 to 4, characterized in that the binder solids are present in an amount of 0.1 to 15%, preferably 1.0 to 15% by weight, based on the weight of the stock. Process according to one of Claims 1 to 5, characterized in that the aqueous papermaking pulp contains cellulose pulp and a mineral filler. 30 A method according to claim 6, characterized in that the amount of cellulose pulp in the pulp is adjusted so that the finished paper contains at least 50% by weight of cellulose fibers. Process according to Claim 6 or 7, characterized in that the binder solids are present in an amount of about 0.5 to 25%, preferably 2.5 to 15% by weight, based on the weight of the mineral filler. Process according to Claim 6, 7 or 8, characterized in that the colloidal silicic acid is added and mixed with the mineral filler before the mineral filler is added to the pulp, and in that guar gum and any cationic starch present are mixed into a mixture of stock, filler and colloidal silicic acid. . Process according to one of Claims 1 to 8, characterized in that a part of the colloidal silicic acid is mixed into the pulp, followed by guar gum and any cationic starch present in the pulp containing the initial part of the colloidal silicic acid, and after agglomeration is formed and mixed the remaining 15 parts of colloidal silicic acid into the pulp before forming the sheet. Process according to claim 10, characterized in that about 20 to about 90%, preferably about 30 to 80% of colloidal silicic acid is added to the pulp to form an agglomerate, and that the remaining part of the colloidal silicic acid 20 is added after the formation of the agglomerate. 12. An improved paper product containing cellulosic cultures, preferably at least 50% by weight of the paper product and characterized in that it has improved strength properties, characterized in that the bond between the cellulosic fibers is improved by a binder containing colloidal silicic acid and guar gum and optionally also a cationic starch complex having a degree of starch substitution of at least 0.01, preferably about 0.01 to about 0.05 and especially about 0.02 to about 0.04, and wherein the ratio (guar gum + cationic starch) ) :( SiO 2) is 0.1: 1 to 25: 1, preferably 0.25: 1 to 12.5: 1. 28 70954